Hot-melt adhesives are widely used for manufacturing disposal diapers, binding books and packaging various products. Examples of the material of the hot-melt adhesives include Styrene-Butadiene-Styrene block copolymer (referred to as SBS hereinafter), Styrene-Isoprene-Styrene block copolymer (referred to as SIS hereinafter), Ethylene Vinyl Acetate block copolymer (referred to as EVA hereinafter) and Amorphous PolyAlpha-Olefin (referred to as APAO hereinafter). A tackifier in a form of a hydrogenated petroleum resin is blended in the base polymer.
The hydrogenated petroleum resin is produced by a hydrogenation process for hydrogenating a polymer obtained by adding styrene monomer to cyclopentadiene as disclosed in Patent Literature 1, for instance. The hydrogenated petroleum resin is sometimes provided in a form of hemispherical pellets in view of handleability.
In producing the hydrogenated petroleum resin, a batch processing in which the pelletized hydrogenated petroleum resin is analyzed and polymerization conditions and hydrogenating conditions are adjusted based on the results of the analysis is performed to produce a hydrogenated petroleum resin of predetermined physical properties.
However, in order to produce hydrogenated petroleum resin pellets of desired physical properties, such a batch processing requires repetition of the adjustment of the production conditions based on the results of the analysis of the produced pellet, and, consequently, requires much production time and complicated work. Accordingly, simplification of production management has been desired.
In view of the above, as disclosed in Patent Literatures 2 to 4 for instance, some of known processes employ a near-infrared spectrometer in producing a synthetic resin to measure an absorption spectrum in the resin that is under production for predicting the physical properties of the final products to control the production process.